Lexmark 1020 printer causes vsndsys.386 to be lost at startup

System:

Old (very old!) Zeos computer
OS: Win 98SE
Printer: Lexmark 1020 Color Jet
Sound Card: Turtle Beach Monte Carlo 929 (I think, but could be 928)

Situation:
This computer was passed on to me by a neighbour, and I have passed it on to
my mother. I don't have the original sound card installation disks though
these are provided on the TB website. My mother lives 3 hours drive away so I
only see this computer from time to time - can't troubleshoot on the spot, so
appreciate as much info as possible to try alternative solutions on next
visit.

Problem:

I can install the sound card drivers and have the sound work fine. I
installed the printer and it works fine. However it appears that each time
the printer is used that the next Windows restart brings up the "vsndsys.386
not found" error message, which has to be clicked "OK" 3 times to close and
bring up normal windows desktop, which is then functional, including the
printer - only the sound is lost.

If I then reinstall the sound card drivers again, all is well again with the
sound until the printer is again used.

I don't think it's a IRQ-type conflict, though I can't really be sure. In
the BIOS, the LPT printer port is set to IRQ 7. However I don't really know
what IRQ it is using in Windows as in the IRQ table, there is no IRQ entry
for the LPT port and IRQ 5 and 7 are both shown as free. The sound card has 3
modes of operation: Sound Blaster Pro in DOS, which uses IRQ 5, Windows Sound
System (WSS mode) for DOS, which uses IRQ 11 and Windows operation - and
again in the Windows IRQ table, there is no entry for the sound card. So I
can't really tell what is happening between the LPT and the sound card in
windows. I can't understand why the Windows IRQ table is not reporting
entries for these things??? !!! Kinda makes it hard to change IRQs if needed.

I'm wondering if it's more like something to do with the fact that for the
sound card, there should be a line device=vsndsys.386 under the [386
enhanced] section of the system.ini file and perhaps when the printer is
deployed it has as part of it's intialisation a string that takes out this
line from system.ini.....? So that when the computer next starts up it
registers it as missing?

Anyone with an inkling about this....your help would be greatly appreciated
as I want my Mum to be able to use both the printer and the sound without
having to worry about this error message all the time.